 To pass the buck means to shift blame or responsibility to someone else and it originates from the game of poker. Poker became popular in America during the 18th century and players were always suspicious of any form of bias or cheating. To stop this, the card dealer was frequently rotated during a game and the person who was next in line to deal was given a marker, which was often a knife. The handles of most knives at the time were made of buck's horn, so the marker became known as a buck.